87aa86845d
Right now, the SCX_WAKE_SYNC logic in rusty is very primitive. We only check to see if the waker CPU's runqueue is empty, and then migrate the wakee there if so. We'll want to expand this to be more thorough, such as: - Checking to see if prev_cpu and waker_cpu share the same LLC when determining where to migrate - Check for whether SCX_WAKE_SYNC migration helps load imbalance between cores - ... Right now all of that code is just a big blob in the middle of rusty_select_cpu(). Let's pull it into its own function to improve readability, and also add some logic to stay on prev_cpu if it shares an LLC with the waker. Signed-off-by: David Vernet <void@manifault.com> |
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scx_rusty
This is a single user-defined scheduler used within sched_ext, which is a Linux kernel feature which enables implementing kernel thread schedulers in BPF and dynamically loading them. Read more about sched_ext.
Overview
A multi-domain, BPF / user space hybrid scheduler. The BPF portion of the scheduler does a simple round robin in each domain, and the user space portion (written in Rust) calculates the load factor of each domain, and informs BPF of how tasks should be load balanced accordingly.
How To Install
Available as a Rust crate: cargo add scx_rusty
Typical Use Case
Rusty is designed to be flexible, and accommodate different architectures and workloads. Various load balancing thresholds (e.g. greediness, frequenty, etc), as well as how Rusty should partition the system into scheduling domains, can be tuned to achieve the optimal configuration for any given system or workload.
Production Ready?
Yes. If tuned correctly, rusty should be performant across various CPU architectures and workloads. Rusty by default creates a separate scheduling domain per-LLC, so its default configuration may be performant as well. Note however that scx_rusty does not yet disambiguate between LLCs in different NUMA nodes, so it may perform better on multi-CCX machines where all the LLCs share the same socket, as opposed to multi-socket machines.
Note as well that you may run into an issue with infeasible weights, where a task with a very high weight may cause the scheduler to incorrectly leave cores idle because it thinks they're necessary to accommodate the compute for a single task. This can also happen in CFS, and should soon be addressed for scx_rusty.